Are you perhaps mounting that second disk read-only?? That would prevent FreeBSD from checking it and marking it clean. You need to run a fsck on the filesystem: but we need to know what filesystem it is before we advise you further.

__________________The only dumb question is a question not asked.
The only dumb answer is an answer not given.

It is UFS and it is not mounted as read only, anyway problem seems to disappear automatically after 3-4 reboots and I don't seeit any more. I think problem might have been because of power failure and hopefully I wont see it again .

Ah... i was messing with filesystems....
I increased my swap, after once, i had none, and used convert *.jpg *.png (or something like that)
and then suddenly X hanged..... I discovered that i was out of mem....

However now i have 2GB SWAP, which is still a lot.... but at some point i might use it for other purposes, when necessary